CN1409448A

CN1409448A - Bead lattice array connector

Info

Publication number: CN1409448A
Application number: CN02143785.8A
Authority: CN
Inventors: 白井浩史; 久保晶
Original assignee: Tyco Electronics AMP KK
Current assignee: TE Connectivity Corp
Priority date: 2001-10-03
Filing date: 2002-09-30
Publication date: 2003-04-09
Anticipated expiration: 2022-09-30
Also published as: TW579107U; SG114573A1; JP3708470B2; JP2003115334A; US6743039B2; CN1311593C; US20030068917A1

Abstract

A ball grid array connector having an insulative housing with a plurality of contacts in electrical connection with corresponding solder balls that protrude from a surface of the housing. The solder balls form a soldering region for attachment to a circuit board. The housing has a center of gravity biased from a center of the soldering region, and a positional compensation member is attached to the housing and the circuit board. The positional compensation member prevents the housing from becoming inclined with respect to the circuit board when the solder balls are attached to the circuit board and prevents the housing from becoming inclined with respect to an electronic part when the electronic part is mounted to the housing on a side opposite from the circuit board.

Description

Ball grid array connector

Technical Field

The present invention relates to electrical connectors and, in particular, to ball grid array connectors having a plurality of solder balls for surface mounting, the connectors being intended for connection to electrical (electronic) components having a pin grid array.

Background

The IC package insert disclosed in japanese unexamined patent application publication No.2000-357572 is a well-known example of a ball grid array connector. The package includes a base housing having a plurality of contacts arranged in a matrix, and a sliding cover housing having openings corresponding to the contacts. The contacts are connected to a printed circuit board (hereinafter simply referred to as a circuit board) by solder balls or tines. An IC assembly having a pin grid array is mounted to the cover housing for connection with contacts on the base housing. Since the IC package has an extremely large number of electrodes, the connection resistance between the pins and the contacts is large. Therefore, after the pins as the electrodes of the IC package are inserted into the openings of the cover case without resistance, the cover case on which the IC package is mounted is slid by the power assist mechanism, and the electrical connection between the contacts and the pins is performed.

As a mechanism for sliding the cover case, a driving mechanism using the principle of a lever is provided at the end of the insert. For this drive mechanism, a large amount of force is required to slide the cover shell to connect the pins and contacts. Thus, the drive mechanism is operated by a tool such as a screwdriver. In this way, a large force is applied to the lever operating portion in the drive mechanism. Therefore, from the viewpoint of durability, metal parts are used for operating the parts of the drive mechanism.

With the aforementioned conventional technique, the center of gravity of the insert is offset at the end of the insert due to the presence of the drive mechanism using heavy metal parts. In other words, the center of gravity of the card is at a position offset toward the drive mechanism side, which is opposite to the center of the contact area or solder ball area (solder area) soldered to the circuit board to fix the card thereto.

Due to the misalignment between the center of the soldering region and the center of gravity of the card, the following problems may occur during the process of reflow soldering the connector to the circuit board. That is, during reflow soldering, a torque is generated which will cause the heavier drive mechanism side to approach the circuit board and the lighter card end on the opposite side to separate from the circuit board. As a result, there is a possibility that the card mounted on the circuit board is inclined thereto, causing the electrical connection to fail. In addition, there is a case where a heat sink is mounted thereon after the IC package is mounted to dissipate heat. In the case where the heat sink is of a circuit board mounting type which is mounted on a circuit board parallel thereto, there arises a problem that the heat sink does not properly contact the inclined surface of the IC package mounted on the inclined package, and a sufficient heat radiation effect is not obtained. In particular, recent computer CPUs operate at high speeds and the amount of heat generated by the CPUs is greatly increased. However, where heat dissipation is insufficient, catastrophic consequences to the operation of the CPU may occur.

In addition, there are cases in which the circuit board is subjected to an additional reflow soldering process in order to mount electronic (electrical) components on the other side thereof. In this process, the aforementioned insert, which has been soldered to the circuit board, is suspended on its underside, that is to say from it, while the electronic components are mounted on the upper surface of the circuit board. During this subsequent reflow soldering process, as the ambient temperature in the vicinity of the circuit board increases, the soldering portions (soldering portions of the contact teeth or solder ball portions) of the card soften and melt. In general, the melted soldered connection portion maintains the mounted state of the circuit board due to surface tension. However, if the center of gravity of the aforementioned insert is misaligned from the center of the soldering region, a torque is generated by the heavy drive mechanism, so that the end portion on the drive mechanism side is separated from the circuit board. Therefore, the card is inclined with respect to the circuit board, and there is a possibility that the card is fixed to the circuit board in this state. Due to this, there is a possibility that connection failure occurs or the card itself is separated from the circuit board.

Disclosure of Invention

The present invention has been developed in view of the above problems. It is an object of the present invention to provide a ball grid array connector which enables reflow soldering of the connector parallel to a circuit board even in the case where the center of gravity of the housing assembly is offset from the center of the area where the solder balls are arranged (soldering area).

It is another object of the present invention to provide a ball grid array connector to which a circuit board mounting type heat sink can be attached to obtain a sufficient heat dissipation effect.

The ball grid array connector of the present invention comprises:

a plurality of contacts for contacting another connector;

an insulative housing for receiving the contacts;

solder balls arranged corresponding to the contacts on the bottom surface of the insulating housing so that they are in electrically conductive connection with the contacts;

a housing assembly soldered to the circuit board by a solder ball, the housing assembly having a center of gravity offset from a center of an area in which the solder ball is disposed; wherein,

a position compensation element is provided to resist tilting of the housing assembly that separates the solder balls from the circuit board due to torque generated by the offset center of gravity during reflow soldering of the housing assembly to the circuit board.

The position compensation element may be, for example, a metal solder plug soldered to the surface of the circuit board, protruding from an end of the housing assembly on the side of the center of gravity of the housing assembly toward the circuit board.

In addition, a structure may be adopted in which the housing assembly includes:

a base shell;

a cover housing slidably mounted on the base housing for receiving the IC package thereon;

a cam member on the front end of the housing assembly for sliding the cover housing; and

a base plate fixed to the base housing for supporting the cam member; wherein,

the flux plug is integrally formed with the substrate.

In addition, the position compensation element may be configured to be placed on the bottom surface of the housing assembly on the side of the center of gravity of the housing assembly.

In the ball grid array connector of the present invention, the center of gravity of the housing assembly is offset from the center of the area where the solder balls are arranged. However, providing a position compensation element on the housing assembly serves to resist tilting of the housing assembly, which separates the solder balls from the circuit board, due to the torque generated by the offset center of gravity. This structure has the following advantageous effects.

That is, even in the case where the center of the land and the center of gravity of the housing assembly are misaligned, the connector can be reflow-soldered to the circuit board in parallel, and the electrical connection between the connector and the circuit board can be reliably established. This effect is particularly interesting where additional electrical components are reflow soldered to the surface of the circuit board. That is, the position compensation element maintains a parallel mounting position to the circuit board without the possibility of the connector separating therefrom.

In addition, where the position compensating element is configured as a solder plug soldered to the surface of the circuit board, projecting from an end of the housing assembly on the side of its center of gravity toward the circuit board, the tendency of the housing assembly to tilt relative to the circuit board due to the torque causing the solder balls to separate from the circuit board is prevented by the solder plug, which projects toward the circuit board, against the circuit board. The position compensation element can therefore be produced in simple components.

Further, in this case, the housing assembly includes:

a base shell;

a cam member on the front end of the housing assembly for sliding the cover housing;

a base plate fixed to the base housing for supporting the cam member; wherein,

the flux plug is formed integrally with the substrate, and the number of parts can be reduced by adopting a structure of commonly used parts. In addition, a circuit board mounted heat sink may be mounted parallel to the circuit board with appropriate surface contacts and IC components to obtain sufficient heat dissipation.

In addition, where the position compensation element is configured to be placed on the bottom surface of the housing assembly on the side of the center of gravity thereof, the position compensation element does not protrude outside the periphery of the connector. Thus, the area occupied by the connector can be minimized.

Drawings

FIG. 1 is a plan view of the connector of the present invention;

FIG. 2 is a vertical cross-sectional view of the connector shown in FIG. 1, taken along line 2-2 of FIG. 1;

FIG. 3 is a side view illustrating the position of the connector of FIG. 1 during a first reflow soldering operation;

FIG. 4 is a side view illustrating the position of the connector of FIG. 1 during a second reflow soldering operation; and

fig. 5A and 5B are side views showing that a connector having an IC package and a heat sink mounted thereon is mounted on a circuit board, wherein fig. 5A shows a state where the connector is not properly mounted on the circuit board, and fig. 5B shows a state where the connector is properly mounted on the circuit board.

Detailed Description

Hereinafter, a preferred embodiment of the ball grid array connector (hereinafter simply referred to as a connector) of the present invention will be described with reference to the drawings. Fig. 1 is a plan view of the connector of the present invention. Fig. 2 is a vertical cross-sectional view of the connector shown in fig. 1, taken along line 2-2 of fig. 1. Fig. 3 is a side view illustrating the position of the connector shown in fig. 1 during a first reflow soldering operation. Fig. 4 is a side view illustrating the position of the connector shown in fig. 1 during a second reflow soldering operation. Fig. 5A and 5B are side views showing that a connector having an IC package and a heat sink mounted thereon is mounted on a circuit board, wherein fig. 5A shows a state where the connector is not properly mounted on the circuit board, and fig. 5B shows a state where the connector is properly mounted on the circuit board.

First, description is made with reference to fig. 1 and 2. As shown most clearly in fig. 2, the connector 1 comprises an insulating base housing (insulating housing) 2 and a cover housing 4 which is slidably arranged on the base housing 2. A plurality of contacts (not shown) as electrodes are arranged in a matrix form on the base case 2. Each of these contacts is electrically connected with a solder ball 6 to be soldered to the circuit board 100 (fig. 2). That is, the solder balls 6 are arranged in a matrix on the base case 2 corresponding to the contacts. The bracket 54 slightly protrudes from the bottom surface 8 of the base housing 2 and is integrally formed with the base housing 2 at the end 50 of the base housing 2. The solder balls 6 protrude from the bottom surface 8 of the base case 2 toward the circuit board 100 slightly longer than the support 54.

In addition, a drive mechanism 14 for sliding the cover housing 4 along the upper surface of the base housing 2 is provided at the end portion 50, which is apart from the ball grid array connector 1, that is, a plurality of regions 10 (lands) where the balls 6 are soldered are arranged. The drive mechanism 14 is similar to the mechanism disclosed in japanese unexamined patent application No.2000-173735 that uses a metal eccentric cam member.

The basic structure of the drive mechanism 14 is explained below. A recess 16 is formed in the bottom surface 8 of the base housing 2 at the end 50 forming the shelf 54. A recess 18 is formed in the upper surface of the base housing corresponding to the recess 16, in which a substrate (described below) with a solder plug 20 is arranged. The recess 16 and the recess 18 communicate with each other through a hole 26. A notch 22 is formed in the cover case 4 at a portion corresponding to the recess 18. A metal plate 24 having a hole 24a formed therethrough is secured within the indentation 22.

A metal cam member 28 is inserted through the apertures 24a and 26 and mounted to construct the housing assembly 42. Cam member 28 has a flange 32 with a tool engaging slot 30 (fig. 1) in its upper surface, and a stem portion 34 extending downwardly from approximately the center of the lower surface of flange portion 32. The trunk portion 34 is inserted through the hole 24a of the metal plate 24, the hole 20a of the base plate 19, and the hole 26 of the base case. Stem 34 projects into recess 16 and a washer 38 is secured at its tip to prevent its withdrawal. The cam member 28 is rotatably supported by the hole 20a of the base plate 19.

Due to the formation of the recess, the base plate 19 reinforces the thinned portion of the base shell, while also serving to support the cam member 28. Since the cam member 28 must be reliably supported with respect to the base housing 2, the base plate 19, although not shown in the drawings, has a rectangular shape extending to the vicinities of both edges of one end of the connector on both sides of the solder key 20. The base plate 19 is thus configured to support the forces exerted by the cam elements 28 over a large area of the base housing 2. A cam 40 is formed at a portion of the periphery of the stem 34 corresponding to the metal plate 24. This arrangement causes cam 40 to cam engage and drive metal plate 24 as cam member 28 rotates. The metal plate 24 slides the cover case 4.

The solder peg 20, which serves as a position-compensating element, comprises a flat portion 48, which is arranged in the recess 18 of the base housing 2, that is to say, part of the base plate 19; the tooth portion 52 extending outward from the end portion 50 of the base case is bent toward the circuit board 100 and then extends substantially parallel to the circuit board 100. The tooth portion 52 has a notch 52 a. The cutouts 52a serve to increase the length of the solder fillet formed when the teeth 52 are soldered to the circuit board. That is, the length of the outer periphery of the tooth portion 52 is increased. This structure is employed to increase the surface tension of the molten solder. The tooth portion 52 protrudes slightly more toward the circuit board 100 than the above-described holder 54.

As best shown in fig. 1, a plurality of openings 44 for receiving pins (electrodes) of an IC package 90 (fig. 5) are arranged in a matrix on the upper surface of the cover case 4, which correspond to the lands 10. In fig. 1, only the outermost and innermost openings 44 are shown, with the middle portion omitted. If the center of the welding zone 10 is indicated by C, the center of gravity G of the housing assembly 42 is in a position offset from the center C toward the drive mechanism 14. This is because the drive mechanism 14 is provided with the metal plate 24 and the cam member 28, which contribute to its weight. If this position is indicated with G, it is a position offset from the center C, as shown in FIGS. 1 and 2.

The process of soldering the housing assembly 42 to the circuit board 100 is explained below with reference to fig. 3 and 4. During reflow soldering, the housing assembly 42 is in a state in which it is merely placed on the circuit board 100 without support, as shown in fig. 3. When the ambient temperature reaches the melting temperature of the solder ball 6, the solder ball 6 starts to melt, and the solder ball 6 is fused with the conductive pad at a predetermined position of the circuit board. At this time, because the center of gravity G is offset from the center C of the welding zone, a torque is generated in the direction indicated by the arrow M1 at the end 50 of the base shell 2. There is a possibility that the end portion 50 sinks with respect to the circuit board 100. In other words, there is a possibility that the right side of the housing assembly 42 becomes lower as shown in fig. 3, while the left side is raised.

However, the tooth portions 52 of the flux plug 20 protrude toward the circuit board 100 and are soldered thereto. The teeth 52 thus resist sinking of the end 50 while the upper surface 46 of the housing assembly 42 remains parallel to the circuit board. Then, when the reflow soldering process is completed, the melted solder balls 16 harden, securing the housing assembly 42 to the circuit board 100. In this process, the solder plugs are used for a similar purpose as the bracket, but they are different in that they are soldered and fixed to the circuit board. The importance of the function of the solder plug 20 will be further explained in the following description of the second reflow soldering process.

The state of the connector 1 during the second reflow soldering process is explained below with reference to fig. 4. A second reflow soldering process is used to mount another electronic component 104 on the surface 102 of the circuit board 100, which is opposite to the side on which the connector 1 has been mounted. The electronic component 104 is placed on the circuit board 100 and surface-mounted thereon in a high-temperature environment in the same manner as described above. At this time, however, the soldered portion of the connector 1 is also exposed to high temperature and thus softened. Since the center of gravity G is offset from the center C of the land, a torque is generated in the direction indicated by the arrow M2 opposite to the arrow M1, making the left side of the connector 1 lower as shown in fig. 4. Therefore, the solder ball 6a near the end 50 of the base housing 2 risks being separated from the circuit board 100, making the connection therebetween unstable. If the reflow soldering process is completed in this state, the connector 1 will be fixed to the circuit board 100 in a state where it is tilted with respect to the circuit board. In the worst case, the parts of the soldering started with the solder ball 6a are separated in order, and the connector 1 may fall off the circuit board 100 during the reflow soldering.

However, since the tooth portion 52 of the solder key 20 described above has a relatively large area, it is firmly soldered to the circuit board 100 even if the torque M2 is generated, and therefore, the connector 1 does not change its position due to the surface tension of the tooth portion 52. Thus, the upper surface 46 maintains a parallel relationship with the circuit board 100. In this manner, the solder plug 20 performs an important function of controlling the position of the connector 1 during reflow soldering. In this regard, the solder plug 20 has a completely different function from a conventional solder plug, which is generally used to mount only electronic parts and the like onto a circuit board.

Next, a state in which the IC package 90 and the heat sink 92 are mounted on the connector 1 is described with reference to fig. 5A and 5B. As shown in fig. 5A, in a state where the connector 1 is not properly mounted on the circuit board 100, the electrical connection between the solder balls 6 of the connector 1 and the circuit board 100 becomes unstable, and at the same time, the upper surface 90a of the IC package 90 is also inclined with respect to the circuit board 100. Therefore, the bottom surface 94 of the heat sink 92 mounted in parallel with the circuit board 100 is not in surface contact with the upper surface 90a of the IC package 90, and it is understood that a sufficient heat dissipation effect cannot be obtained.

As shown in fig. 5B, the position of the connector 1 is properly maintained in a state where the connector is properly mounted on the circuit board 100. In this state, the upper surface 46 of the housing assembly 42, the upper surface 90a of the IC assembly 90, and the bottom surface 94 of the heat sink 92 are parallel with respect to the circuit board 100. Thus, a highly reliable electrical connection is obtained. In addition, a sufficient heat dissipation effect is obtained due to the surface contact between the upper surface 90a of the IC package 90 and the bottom surface 94 of the heat sink 92.

Next, examples of the present invention will be described.

Examples

For satisfactory performance, it is necessary that the connector 1 has a tilt angle in the range of ± 0.2 °. For the connector of the present invention, different heights were set for the solder plugs 20, and 13 experiments were performed for each height. The results are given in Table 1 below:

TABLE 1

Measurement of connector tilt angle

Height between the holder and the flux plug	0.1mm	0.2mm	0.3mm
Height between the holder and the flux plug	0.1mm	0.2mm	0.3mm	After the first reflow soldering	0.18°～-0.07°	-0.16°～-0.02°	-0.11°～+0.05°
After the second reflow soldering	-0.05°～+0.16°	-0.15°～0°	-0.08°～+0.13°	After the first reflow soldering	0.18°～-0.07°	-0.16°～-0.02°	-0.11°～+0.05°

Note that: the direction in which the drive mechanism side is separated from the circuit board is designated as positive (+), and the direction in which the drive mechanism side approaches the circuit board is designated as negative (-). In addition, the protruding height of the bracket 54 from the bottom surface 8 of the base case 2 is 0.1mm, and the protruding height of the solder ball 6 from the bracket 54 is 0.25 mm.

From the above experimental results, it was confirmed that the tilt angle of the connector 1 is well within the range of ± 0.2 ° in the case where the height of the solder plug 20 above the holder 54 is 0.1mm, 0.2mm, and 0.3 mm.

The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments. For example, the drive mechanism may not be a mechanism operated by a flat-head screwdriver, but may be a known structure that additionally uses a lever. In addition, the above embodiments relate to an interposer that is an IC package. However, it goes without saying that the present invention may be applied to an electrical connector using a surface-mounted ball grid array having a plurality of electrodes connected to another connector.

The flux plug 20 is not limited to a plug having a single cutout 52 a. A plurality of cuts may be provided. In addition, the position of the drive mechanism need not be on the central axis of the connector 1. The drive mechanism may be placed in any desired position ranging, for example, from the upper right position to the lower left position of fig. 1.

For the above-described embodiment of the present invention, a case is explained in which the flux plug 20 as a position compensation element is provided at the end 50 of the base housing 2. Alternatively, the flux plug 20 may be provided at the end opposite the end 50. In addition, a relatively heavy attachment may be mounted at the end opposite to where the drive mechanism is mounted. Alternatively, a heavier part may be formed integrally with the base housing 2 and/or the cover housing 4.

Claims

1. A ball grid array connector comprising:

a plurality of contacts for connecting to another connector;

an insulating housing for receiving said contacts;

solder balls arranged corresponding to the contacts on the bottom surface of the insulating housing so that they are conductively connected to the contacts;

a housing assembly soldered to the circuit board by the solder balls, the housing assembly having a center of gravity offset from a center of an area in which the solder balls are disposed; wherein,

a position compensation element is provided on the housing assembly for resisting tilting of the housing assembly which separates the solder balls from the circuit board, the tilting being caused by a torque generated by the offset center of gravity during reflow soldering of the housing assembly to the circuit board.

2. A ball grid array connector as set forth in claim 1, wherein said position compensating member is a metal solder plug soldered to a surface of said circuit board and projecting from an end of the housing assembly on said center of gravity side thereof toward said circuit board.

3. A ball grid array connector according to claim 2,

the housing assembly includes:

a base shell;

a cover housing slidably mounted on said base housing for receiving an IC package thereon;

a cam member on a front end portion of the housing assembly for sliding the cover housing; and

a base plate fixed to the base housing for supporting the cam member; wherein,

the flux plug is integrally formed with the substrate.

4. A ball grid array connector according to claim 1,

the position compensation element is placed on a bottom surface of the case assembly on the gravity center side thereof.